In the filter holders of this type, the device for height adjustment generally comprises a complicated system of rods requiring locking at different heights so as to find the precise positions of the perforated bottom in the cage of the cup. Thus, in the machines of the "Espresso" type, the pressure of the hot water supplied by the machine pump being about 15 bars, it is imperative that the perforated bottom be maintained locked at different heights during the infusion operation so as to guarantee the choice of infusion selected by the user, and to avoid any abrupt decompression which would give rise to the destruction of the filter holder and with risk of projection of hot steam and an infusion outside the filter.
Moreover, devices have been proposed for locking with a screw-nut assembly, but as will be understood, the adjustment as to height becomes long, difficult and imprecise during passage from one infusion operation according to a choice of cups, to another infusion operation with another choice of cups.